Using SAR and optical data from Sentinel satellites for precise modeling of seasonal floating reed islands dynamics in Srebarna Lake

The present study is a continuation of the previous monitoring studies on floating reed islands based on remote sensing methods, but this time the study is much more precise in order to create a sustainable operating model for subsequent monitoring studies on this specific type of habitats. The aim of this study is to create a precise model for the movement and dynamic of the floating reed islands in Srebarna Lake. This was done by creating a hybrid model (based on optical and SAR data), assessing the actually condition of floating reed islands, and applying it to quantify of the movement of floating reed islands to perform an actual and seasonal habitats monitoring. To create the hybrid model, the advantages of SAR data-Sentinel-1 for the hydrological dynamics monitoring of Srebarna Lake were used. The SAR data used were obtained for different time periods, within the observed seasons. Multispectral satellite data from Sentinel-2 was also used in order to apply an orthogonal transformation model called Tasselled Cap Transformation (TCT). The Tasselled Cap model is a very effective method for classifying and analyzing processes related to the dynamics of changes affecting the main components of the Earth's surface: soil, water, and vegetation. This model proved to be very effective in recognizing specific types of vegetation and habitats, such as floating reed islands and their transformation over a period of time. The results for the reconciliation of TCT images and SAR data define very well the precise boundaries of both the central water body in Srebarna Lake, and the floating reed islands. The results obtained by means of comparative analysis confirm both methods as being equally effective to determine the floating reed islands dynamics in the hybrid model proposed in this study.